Keyboard



FIG. 1 is a front elevational view of a keyboard showing my new design;

FIG. 2 is a left side view thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a top plan view thereof; and,

FIG. 5 is a bottom plan view thereof.

The broken lines shown form no part of the claimed design. 

The ornamental design for a keyboard, as shown and described. 